It has been a long-standing goal in the health care community to integrate advanced communications systems with information processing systems to provide superior medical services. Various devices have been developed that enable medical data to be obtained for improving the monitoring of medical conditions of patients thus providing an earlier warning of possible distress.
By way of example, U.S. Pat. No. 4,004,577 discloses a method for treating coronary-prone patients when heart attack symptoms occur before qualified direct contact personal care can be administered. In this patent, a device provides auditory signals indicative of the existing heartbeat, and telephone communication is established between the patient and a remote center, capable of making a qualified response based on the auditory signals.
Another example is U.S. Pat. No. 4,712,562, that discloses a system and method for obtaining from a patient's body information pertaining to the patient's blood pressure and heart rate, and generates signals representative thereof in a form suitable for telephonic communication, and transmits these signals to a remote central digital processor for storage and analysis. The data resulting from the analysis is submitted to the patient or physician. Similar systems are disclosed in U.S. Pat. Nos. 3,724,455 and 5,007,429. All of the above patents disclose non-invasive measurements that are to be performed at home (typically by the patient himself). The scope of medical information that can be thus gathered from a patient and transmitted to a remote medical center is limited.
Important medical indications can be measured by blood analysis. It is known from U.S. Pat. No. 6,071,251 for example, to monitor levels of Glucose in the blood as an indication of diabetes. For diagnosing various cardiac conditions, particularly damage to the heart muscle, it is known to measure levels of Troponin T, Troponin I and Myoglobin in the blood.
Blood sampling and analyses are usually performed in a hospital or laboratory. Typically, the test is not performed by the patient himself but rather by professional personnel. The blood sample can either be analyzed immediately or, at a later time and at a different location from where it is sampled. Usually blood is drawn by vacuum by means of either a manual or automated process. The test may be performed either in situ or at a remote location.
The use of vacuum for blood extraction is exemplified in U.S. Pat. No. 4,396,023, which discloses an apparatus for obtaining blood samples from the tails of animals, such as mice or rats. The tail is nicked or transected and then placed in a single-use vacuum tube connected to a one-hole rubber stopper. The vacuum is communicated into the interior of the tube via a hole therein and promotes the flow of blood from the tail. When the desired volume of blood has been collected, the vacuum is turned off and the animal is removed.
The use of a vacuum for blood extraction is also exemplified in U.S. Pat. No. 5,320,607, which discloses a leech-like skin-adhesive blood sampling device comprising a sealed vacuum chamber in a state of pre-existing reduced pressure, a piercing means and means for collecting the drawn blood. However, this patent does not disclose the possibility to control the operation of the device in accordance with the quantity of the drawn blood.
In several patents to Abbot Laboratories, particularly U.S. Pat. No. 6,071,251 a method and apparatus for obtaining blood for diagnostic testing is disclosed. In the above patent, an opening in the skin is made and a vacuum is used to aid in extracting the sample of blood. The vacuum is applied to the surface of the skin in the vicinity of the opening, causing the site to become engorged with blood and the skin to become more stretched. As a result, the skin rises up to a position where it seals the vacuum chamber, after which it is pricked by a lancet assembly. The blood is then drawn to a strip capable of detecting analytes therein. The detecting strip is positioned near the site of the opening of the skin (no more than a few millimeters), so there is physical contact between the blood extracted and the strip, a minute quantity of blood being absorbed by the chemical strip and diffused through the layers thereof. To this end, a special multi-layer chemical strip must be used and the device is not suitable for use with standard chemical strips, which on the other hand, require a larger quantity of blood, typically several drops (quantities in the range of 150-200 micro-liters of blood) usually sampled in a separate process, by professional personnel. Thus, it would be of advantage, for the purpose of self-sampling and testing of blood, to utilize a common and standard chemical test strip.
U.S. Pat. No. 3,634,039 discloses a blood-testing device that enables a predetermined amount of blood to be withdrawn as a function of the number of tests to be performed. U.S. Pat. No. 5,035,865 discloses a vacuum blood sample-collecting device which includes means for measuring the amount of collected blood in the blood container. Neither patent discloses an apparatus for predetermining or measuring a small quantity of blood, such as a few drops.
U.S. Pat. No. 4,493,710 discloses a drip-rate sensing means which is included in an intravenous drip-rate controller device for use in controlling the drip rate of a solution from an intravenous container into the vein. U.S. Pat. No. 4,261,388 discloses a liquid drip-rate controller including an optical sensor for controlling the flow of fluid from an infusion fluid reservoir to an intravenous infusion site. Neither patent discloses a device capable of counting drops of blood drawn from the vein.
There is a need in the art for a device that would enable a patient to perform a blood test and analysis on his own (or with the help of a non-professional), and that would require withdrawal of only several drops of blood.